Tee connection to a pipeline

ABSTRACT

A method for securing a branch assembly to a pipeline includes positioning a first containment ring surrounding an area from which the branch is to extend, positioning a first annular seal within the containment ring to provide a first ring/seal arrangement, positioning a second containment ring spaced from the first containment ring and first annular seal, positioning a second annular seal within the second containment ring to provide a second ring/seal arrangement, positioning the second part of the branch assembly onto the seals, and positioning a first part of the assembly on the pipe line and securing the first and second parts together so as to leave an annular gap between the first and second ring/seal arrangements and to provide an access point or vent in the second part communicating with the annular gap.

BACKGROUND OF THE INVENTION

(1) Field of the Invention

The present invention relates to tee or branch connections to a pipelineand, more particularly, to a method of connecting tee or branchassemblies to pipelines such as hydrocarbons, for example crude oil ornatural gas, or water mains.

(2) Description of Related Art

An existing technique for repairing damaged steel pipelines usesbasically two half-shells which are secured together to form a shellassembly which encircles the pipeline leaving an annulus between thepipeline and the shell assembly which may be filled with grout thatbonds the shell assembly to the pipeline wall. The grout thus fills andsurrounds the damaged region and supports the damaged pipeline wall.Alternatively, the shell assembly may be secured by welding to thepipeline.

An object of the present invention is to provide a method of securingtee or branch connections to pipelines.

BRIEF SUMMARY OF THE INVENTION

According to the invention, a method is provided for securing a branchassembly to a pipeline, wherein the branch assembly comprises a firstpart for locating on the side of the pipeline remote from the side fromwhich the branch is to extend, and a second part incorporating thebranch, the method comprising positioning a first containment ring onthe pipeline at the required position on the pipeline and surroundingthe area from which the branch is to extend, positioning a first annularseal on the pipeline so that the seal is wholly radially within thecontainment ring to provide a first ring/seal arrangement, positioning asecond containment ring on the pipeline spaced from the firstcontainment ring and first annular seal, positioning a second annularseal on the pipeline so that the second seal is wholly radially withinthe second containment ring to provide a second ring/seal arrangement,positioning the second part of the branch assembly onto the seals,positioning the first part of the assembly on the pipeline and securingthe first and second parts together so as to compress the seals andleave an annular space between the first and second parts and theexternal surface of the pipeline, and to leave an annular gap betweenthe first and second ring/seal arrangements, providing an access pointor vent in the second part communicating with the annular gap. Theaccess point or vent allows monitoring of the pressure in the annulargap to check for seal integrity. The vent may include a valve via whichbuild up of pressure of fluid in the annular gap can be released throughthe vent. Once pressure is detected in the annular gap, the vent can beclosed or sealed so that the second seal becomes effective, therebymaintaining the integrity of the branch connection.

Sealing means may be provided for substantially preventing grout fromescaping from the annular space, and grout may be introduced into theannular space that cures to bond the branch assembly in position on thepipeline.

It will be appreciated that subsequent to the branch assembly becomingbonded to the pipeline, a known procedure can be executed for cutting acoupon out of the pipeline via access through the branch under “live”conditions of the pipeline.

It will also be appreciated that the annular seals must be sufficientlycompressible, and also sufficiently robust to withstand and contain withthe containment rings line pressure during operation of the pipelineover the working pressures.

The grout may, for example, be selected from the following range:

urethanes, polyesters, acrylics, epoxies and cementatious compounds. Itwill be appreciated that each should be selected to satisfy theoperating temperature, humidity and curing rate which then leads to thedifferent adhesion strengths for different applications. Different groutmaterial provides a different exothermic reaction which will determinethe volume change after installation. It will also be understood thatthe volume change of epoxy grout should be optimized to minimize theinternal stress system within the grout.

In order to ensure there is a good key for the grout, the externalsurface of pipeline and the inner surface of the first and second partsof the branch assembly may be dressed up or grit blasted prior to theassembly being mounted on the pipeline.

Conveniently, jacking means are employed to space the first part fromthe pipeline when the first and second parts have been secured togetheron the pipeline.

The jacking means may be hydraulically operated. For example, thejacking means may comprise a plurality of jacking members slidablymounted in apertures in the first part and pressure-applying meansmounted with respect to the first part and behind the jacking membersand being urgeable under hydraulic pressure against the jacking membersto cause the jacking members to be urged towards the pipeline topositions to space the first part from the pipeline.

Conveniently, the jacking members are slidably mounted in bosses or thelike secured or fixed to the first part, in which case thepressure-applying members are also slidably mounted in the bosses or thelike.

When the jacking members are in position spacing the first part from thepipeline, stop means are fixed in position with respect to the firstpart to prevent the jacking members moving away from the pipeline.

Advantageously, the pressure-applying means are removably mounted withrespect to the first part, and the stop means are adapted to occupy thepositions occupied by the pressure-applying means when the latter areremoved.

The stop means may be screwed into position in threaded supportingmembers fixed to the first part.

Conveniently, one or more load bearing members are positioned betweenthe pipeline and the jacking members to spread the applied load when thejacking members are in position spacing the first part from thepipeline.

The load bearing members may be in the form of enlarged feet on thejacking members, the surfaces of which feet may generally correspond tothe profile of the pipeline. Alternatively, the load bearing members maybe secured to the pipeline, in positions so that they will be engaged orcontacted by the jacking members.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will now be described, by way of example only, withreference to the accompanying drawings, in which:

FIG. 1 shows schematically the top and bottom parts of a branch assemblyto be used in a method according to the invention;

FIG. 2 is a schematic plan view of a pipeline on which are positionedfirst and second containment rings and associated first and secondannular seals in preparation of the pipeline receiving the top part ofthe branch assembly;

FIG. 3 is a schematic side view of the pipeline on which the top andbottom parts of the branch asssembly have been secured together inposition;

FIG. 4 is a schematic view in the direction of arrow A in FIG. 3;

FIG. 5 is a similar view to that shown in FIG. 4 but of a modifiedarrangement in which the jacking means is hydraulically operated; and

FIG. 6 is a view similar to FIG. 5 but showing stop means occupying thepositions previously occupied by the pressure-applying means, as in FIG.5.

DETAILED DESCRIPTION OF THE INVENTION

With reference to FIG. 1, there is shown a branch assembly 1 comprisinga first part 2 forming the upper part of the assembly and a second part3 forming the lower part.

The upper part and lower parts of the assembly 1 are made of carbonsteel and have generally part cylindrical portions 4 and 5,respectively, which are securable together about a pipeline 6 viaflanges 7 and 8 which extend longitudinally along each side of the upperand lower parts, as can be clearly seen in FIG. 3.

The flanges 7 of the upper part 2 have apertures 9 which are intended toalign with apertures 10 in the flanges 8 of the lower part 3 so thatsecuring bolts 11 (see FIGS. 3 and 4) can be passed therethrough tosecure the two parts 2 and 32 together on the pipeline.

The upper cylindrical portion 4 includes an apertured section 12 fromwhich extends a short branch pipe 13 terminating in an annular flange 14to which a branch pipeline having an end flange can be connected in aknown fashion (not shown) after the assembly 1 is securely bonded to thepipeline 6.

By way of illustration of the invention, a method of securing the teeassembly 1 to a steel pipeline is described below.

Initially, the area of the external surface of the pipeline to which thebranch assembly is to be secured is grit blasted (not shown), as are theinner surfaces of the part-cylindrical portions 4 and 5 of the upper andlower parts of the branch assembly.

First and second containment rings 16 and 116, respectively, ofdifferent diameters and made of steel and shaped so as to conform to theshape of the pipeline are positioned in spaced relationship to eachother on the pipeline around the area 6 a from which the branch pipe 13of the branch is to extend.

First and second annular seals 17 and 117 made for example of rubber orpolymer and metal and of greater thickness than the containment rings 16and 116 are then placed within the first and second containment rings,respectively, so as substantially to conform to the shape of thepipeline 6 (see FIG. 2).

The upper part 2 of the branch assembly is lowered onto the seals 17 and117, with the bore 13 a of the branch pipe 13 being centralised with thearea 6 a surrounded by the inner first seal 17 and associatedcontainment ring 16, the lower part 3 is moved into position on thepipeline, and the upper and lower parts 2 and 3 of the assembly aresecured together by means of bolts 11 used in association with thealigned apertures 9 and 10 in the flanges 7 and 8 (see FIGS. 3 and 4).

It will be appreciated from FIGS. 1 to 4 that the first containment ring16 and associated first annular seal 17 form a first ring/sealarrangement 16/17 that is spaced by an annular gap 118 from a secondring/seal arrangement 116/117 formed by the second containment ring 116and the associated second annular seal 117. The upper part 2 is providedwith a closable vent 119 that allows communication to the annular gap118.

Jacking bolts 18 are mounted in the wall of the lower part 3 of thebranch assembly. These jacking bolts extend through the wall of thelower part to engage or bear on the surface of the pipeline 6, and canbe turned from the outside of the assembly to be loosened or tightenedagainst the wall of the pipeline. The jacking bolts 18 are adjusted sothat the annular seal 17 is sufficiently compressed to provide asuitable seal prior to the introduction of epoxy grout.

Once the tee assembly 1 is in position on the pipeline, a generallycylindrical or annular space 19 is left or defined between the upper andlower parts 2 and 3 and the external surface of the pipeline 6.

The annular space 19 is bounded by sealing means 20, such as suitableputty which is located between the branch assembly and the pipeline atthe opposite ends of the assembly, and by the second annular ring sealarrangement 116/117.

The grout is then injected into the annular space 19 via injectionopening 21, located towards the bottom of the lower part of theassembly, to fill the annular space. An outlet opening 22 for expressedair and excess injected grout is provided in the upper part of theassembly. After the annular space 19 is filled with grout, the grout isallowed to cure and thereby bond the upper and lower parts 2 and 3, andthus the branch assembly 1, to the pipeline.

When the assembly is securely bonded by the grout to the pipeline, thejacking bolts 18 can be, optionally, loosened off to ensure load isfairly or more evenly distributed on the pipeline by the grout.

In FIGS. 5 and 6 an alternative method of jacking is illustrated. Thelower part 3 is provided with apertures 23 in which are slidably mountedjacking members 24 each carrying enlarged feet 25 which match theprofile of the pipeline and are for engaging or contacting the surfaceof the pipeline. Bosses 26 having through bores 27 are secured to thelower part 3. The through bores 27 are for slidably receiving the free,outer ends of the jacking members 24. Hydraulically operated means 28comprising cylinder means 29 are mounted on the bosses 26. Each cylindermeans 29 comprises a cylinder 30 and a pressure-applying means 31 in theform of a piston is slidably mounted in the cylinder 30. The cylinders30 are aligned with respective ones of the bores 27 of the bosses 26.The pistons are also slidably mounted in the bores 27 of the bosses 26.Hydraulic pressure is applied through lines 32, 33, 34 to the respectivecylinders 30 from a common main line 35 to a source 36 of hydraulicpressure. On applying appropriate hydraulic pressure to the cylinders 30the pistons 3 are urged against the jacking members 24 to cause thejacking members to be urged towards and against the pipeline 6 such thatthe annular seal 17 is compressed and a generally annular space or gap19 is formed as described earlier.

The enlarged feet 25 serve as load bearing members that spread the loadapplied to the pipeline via the jacking members.

After the grout has been injected into the annular space 19 and allowedto cure, as described above, the cylinder means 29, including thepistons, are removed from the bosses 26 and stops 37 (see FIG. 6) areinserted into the bosses and fixed in position therein butting upagainst the back ends of the jacking members, thereby occuping thepositions previously occupied by the pistons, to prevent the jackingmembers moving away from the pipeline. The stops 37 may be externallythreaded as at 37 a and screwed into bosses 26 which are correspondinglyinternally threaded as at 26 a. The provision of the fixed stops 37removes reliance on the continued integrity of the cured grout behindthe enlarged feet to prevent unwanted movement of the jacking members 24away from the pipeline. Thus, if the cured grout behind the enlargedfeet 25 should deteriorate and disintegrate or “fail”, the stops 37 holdthe pipeline in position relative to the shell assembly.

The closable vent 119, which may include a valve (not shown), providesan access or monitoring point via which the pressure in the annular gap118 can be checked or monitored by connecting the vent to a pressuremonitor (not shown) and, for example continually or periodically, tocheck for seal integrity. Thus, if for example seal 17 should fail thepressure in the annular gap will build up or increase and be detected asa result of the checking via vent 119. Escape of pressurised fluidcarried by the pipeline as a result of leakage past a failed first seal117 can thus be detected. If such leakage and detection occurs then thevent 119 can be closed or sealed and the second seal 117 the becomeseffective, thus maintaining the integrity of the branch connection.

In a modification (not shown) the enlarged feet on the jacking membersmay be replaced by load bearing members secured to the pipeline inpositions so that they will be engaged or contacted by the jackingmembers.

With the branch assembly securely bonded to the pipeline, known “live”procedures can be performed for cutting out a coupon from area 6 a ofthe pipeline (not shown) and joining a branch pipeline (not shown) tothe branch utilising the branch pipe 13. Such known procedures will notbe described here.

A method according to the invention, examples of which are describedabove, enables a branch assembly to be bonded to a pipeline withouthaving to employ welding techniques. This is a particular advantagewhere “live” pipelines are involved, especially where there are highproduct flow rates through the pipeline. Other advantages of using sucha method include minimising unnecessary pressure reduction in thepipeline and enabling cost savings for installations.

Whilst particular embodiments of the invention have been describedabove, it should be appreciated that various modifications may be madewithout departing from the scope of the invention. For example, theorder in which the first and second containment rings and associatedseals are placed in position on the pipeline may be varied. In addition,one of more further containment rings and seals could be employed in theinvention beyond the first and second ones specifically described.Further, particularly where the branch assembly needs only temporarilyto be connected to the pipeline, grout need not be introduced into theannular space 19 and the annular space 19 need not be bounded by sealingmeans 20, in which case the injection opening 21 could be omitted also.

1. A method for securing a branch assembly to a pipeline, wherein thebranch assembly comprises a first part for locating on a side of thepipeline remote from a side from which the branch is to extend, and asecond part incorporating the branch, the method comprising: positioninga first containment ring on the pipeline at a required position on thepipeline and surrounding an area from which the branch is to extend,positioning a first annular seal on the pipeline so that the seal iswholly radially within the containment ring to provide a first ring/sealarrangement, positioning a second containment ring on the pipelinespaced from the first containment ring and first annular seal,positioning a second annular seal on the pipeline so that the secondseal is wholly radially within the second containment ring to provide asecond ring/seal arrangement, positioning the second part of the branchassembly onto the seals, and positioning the first part of the assemblyon the pipe line and securing the first and second parts together so asto compress the seals and leave an annular space between the first andsecond parts and the external surface of the pipeline, and to leave anannular gap between the first and second ring/seal arrangements,providing an access point or vent in the second part communicating withthe annular gap.
 2. A method as claimed in claim 1, wherein the firstpart forms a lower part of the assembly and second part forms an upperpart of the assembly.
 3. A method as claimed in claim 1, wherein theannular seals are made of rubber or of a polymer and metal composite. 4.A method as claimed in claim 1, wherein grout is injected into theannular space between the first and second parts and the externalsurface of the pipeline.
 5. A method as claimed in claim 1, whereinjacking means are employed to space the first part from the pipelinewhen the first and second parts have been secured together on thepipeline.
 6. A method as claimed in claim 5, in which the jacking meansis hydraulically operated.
 7. A method as claimed in claim 6, in whichthe jacking means comprises a plurality of jacking members slidablymounted in apertures in the first part and pressure-applying meansmounted with respect to the first part and behind the jacking membersand being urgable under hydraulic pressure against the jacking membersto cause the jacking members to be urged towards the pipeline topositions to space the first part from the pipeline.
 8. A method asclaimed in claim 7, in which the jacking members are slidably mounted inbosses secured or fixed to the first part, and the pressure-applyingmembers are also slidably mounted in the bosses or the like.
 9. A methodas claimed in claim 7 or 8, in which when the jacking members are inposition spacing the first part from the pipeline, stop means are fixedin position with respect to the first part to prevent the jackingmembers moving away from the pipeline.
 10. A method as claimed in claim7 or 8, in which the pressure-applying means are removably mounted withrespect to the first part, and the stop means are adapted to occupy thepositions occupied by the pressure-applying means when the latter areremoved.
 11. A method as claimed in claim 10, in which the stop meansare screwed into position in threaded supporting members fixed to thefirst part.
 12. A method as claimed in claim 11, in which one or moreload bearing members are positioned between the pipeline and the jackingmembers to spread the applied load when the jacking members are inposition spacing the first part from the pipeline.
 13. A method asclaimed in claim 12, in which the load bearing members are in the formof enlarged feet on the jacking members.
 14. A method as claimed inclaim 13, in which the surfaces of the feet generally correspond to theprofile of the pipeline.
 15. A method as claimed in claim 12, in whichthe load bearing members are secured to the pipeline in positions sothat they will be engaged or contacted by the jacking members.
 16. Amethod as claimed in claim 1, further comprising providing sealing meansfor substantially preventing grout from escaping from the annular space,and introducing into the annular space grout that cures to bond thebranch assembly in position on the pipeline.
 17. A method as claimed inclaim 1, wherein the access point or vent allows monitoring of thepressure in the annular gap to check for seal integrity.